General

I first tried to keep a dual-boot just in case, but once we disable Raid and put SATA in AHCI mode, Windows can't boot anymore. (later I read it could be possible to fix it by rebooting several times Windows till safe mode is kicked in, but it was too late for me.)

Attention: with versions 1.2.10 through 1.2.16 and older Linux kernels, there is a serious bug that let the screen black after suspend/wake up. The workaround is to set the lightness to the maximum but it breaks further lightness tuning.

Linux kernels 4.8 and below tend to work best with A6 BIOS (1.2.0), although there is a workaround that allows it to work with later versions. This workaround uses the intel_reg utility to reset the "pwm_granuality" setting of the onboard graphics. Solution discussed here: [1]. This issue is reportedly fixed in Linux 4.9, and also in recent Ubuntu 16.10 kernel updates. See the patch here [2].

Even with the intel_reg workaround above, the screen brightness cannot be set to the lowest level without turning the screen off. This is fixed in 1.2.18.

Debian

I kept UEFI so we need a Debian netinstall because liveCD doesn't have UEFI support yet.
But Wi-Fi requires a proprietary firmware:

dd the image on a USB stick and boot it.
It will also complain for a missing brcmfmac43602-pcie.txt but we can safely ignore it. (well I think so, but Wi-Fi has troubles now and then under heavy load, see below)

I chose a guided partitionning of the entire disk, with encrypted LVM containing /, /home and swap. But proposed / was a bit too small IMHO (10G) so I deleted and recreated / (50G) and /home.
Initially I tried to add the "discard" option for the partitions which should help on SSD but the kernel reported that "discard" wasn't supported by the disk.

If you want to backup partition table and partitions before destroying everything, it's the right time!

As bridge, primus or virtualgl can be used. Primus is available in the Debian repos while VirtualGL is here. Using primus currently.

Touchpad

Nothing wrong with the touchpad but its default config is a bit painful especially because it's large and my right palm touches it often, even with the option to diable it when typing and because it's "soft" buttons.
I disabled the button area to limit somehow the problem but still you've to get used to first touch and hold before pressing a button to do a drag and drop and not the opposite.

If this is so, add /etc/modprobe.d/synaptics.conf with this line, cf Kernel section below:

blacklist i2c-designware-platform

Touchscreen

Touchscreen works well but when an external screen is connected, it spans over both screens so e.g. touching the middle of the laptop screen moves the mouse to some middle point of the virtual screen combining both screens.
To fix it, see https://wiki.archlinux.org/index.php/Calibrating_TouchscreenThis example is for an external screen mapped to the right of the laptop screen:

External microphone

With Debian+Cinnamon, the system detects the mic, we can see it in the sound properties and select it, but still the internal mic is used.
When using pavucontrol, selecting the "headset microphone" works fine (it still needs some level boosting).

DA200

DA200 used to be recognized only if it was plugged at boot.
With kernel 4.6 the device is properly detected dynamically.
The adapter is actually using DisplayPort.
VGA output works.

HDMI output is limited to some modes (max 1920x1080, cf Dell support) and by default xrandr will try an unsupported mode.
Even "xrandr --output DP-1 --mode 1920x1080" fails by default.

Some supported modes: 800x600, 1024x768, 1280x720, 1920x1080i
1920x1080i is interlaced and awful to look at.
Reducing the rate allows a non-interlaced 1920x1080 mode, you can test it with:

xrandr --output DP-1 --mode 1920x1080 -r 30

If this works for you, you can create a new mode, using cvt to find the proper parameters:

The USB Billboard Device Class definition describes the methods used to communicate the Alternate Modes supported by a device container to a host system. More details on Billboard Devices are available in the USB Billboard Device Class specification at the following link: http://www.usb.org/developers/docs/devclass_docs/.